In CAD/CAM based techniques for the design and manufacture of dental restorations a digital representation of the dental restoration, herein referred to as a digital restoration design, is generated using Computer Aided Design (CAD) software. Based on the generated digital restoration design the physical restoration is subsequently manufactured using Computer Aided Manufacturing (CAM) equipment.
A dental restoration can be manufactured from a milling block of a dental material, such as Zirconia, by removing milling block material until the remaining part of the milling block has the desired shape of the dental restoration. When manufacturing a dental restoration from a milling block using CAD/CAM techniques, the portions of the milling block which are to be removed can be derived from a digital representation of the multi-shaded milling block and a digital restoration design by means of an electronic data processing device, such as the microprocessor of a computer. In a given relative arrangement of the digital restoration design and the digital representation of the milling block, the former define a sub-volume of the latter such that when the milling block material located outside this sub-volume is removed, e.g. by milling, the dental restoration is formed from the milling block.
The shade of natural teeth usually varies over the tooth surface and dental restorations manufactured from single-shaded milling blocks often cannot mimic the correct aesthetic properties of natural teeth. Multi-shaded dental restorations manufactured from multi-shaded milling blocks can provide a more correct aesthetic appearance than what can be obtained from single-shaded milling blocks. The multi-shaded milling block has a distribution of shades, e.g. a number of parallel layers of different shades, such that the shade profile of the manufactured dental restoration depends on the location of the sub-volume of the milling block from which the dental restoration is manufactured.
Several multi-shaded milling blocks are commercially available ranging from blocks with parallel layers of different shades to milling blocks where the shade distribution is designed to mimic the dentine of a tooth (e.g. VITABLOCS RealLife by Vident) or milling blocks that are crown shaped (e.g. priticrown milling blocks from Pritidenta GmbH).
In CAD/CAM based techniques, the digital representation of the multi-shaded milling block comprises shade data describing the shade distribution of the multi-shaded block. In order to obtain a preferred aesthetic appearance of the dental restoration, the digital restoration design and the digital representation of the multi-shaded milling block must be arranged according to a preferred relative arrangement in which geometry data of the digital restoration design and the shade data are aligned to provide the preferred aesthetic appearance for the manufactured dental restoration. For a milling block with a number of parallel layers of different shades it may e.g. be preferred to manufacture the dental restoration such that the incisal edge or occlusal surface of the dental restoration is substantially parallel with these layers.
US20110125304 describes a dental CAD/CAM system that can generate and display simulated images of the aesthetic properties of a single dental restoration using design data representing the dental restoration, data representing the surface of the dental restoration, data representing the volume of a milling block, and data representing aesthetic properties of the milling block.
However, it remains a problem to provide a method, a system and a user interface for determining preferred relative arrangements of a plurality of digital restoration designs and digital representations of multi-shaded milling blocks where symmetric aesthetic properties are obtained for left-right sets of dental restorations.